Reduction and oxidation reaction is a commonly utilized method to control or measure the concentration of a chemical species of interest. It is widely employed in process control in paper/pulp industry, sanitation control such as swimming pool and drinking water safety, and waste water management. A noble metal sensor, such as platinum and gold is the most commonly used sensor for providing such a measurement. This measurement is commonly known as the oxidation reduction potential (ORP) measurement.
Although generally effective, prior art ORP measurement methods suffer from slow response speed, uncertainty of which of chemical reaction from several that may be occurring gives rise to the oxidation reduction potential, and the lack of ability to distinguish sensor fouling or memory effect from the measurement of the species of interest. For example, a known redox process centering at the intended control point may provide an ORP value of 500 mV. However, if the sensor is fouled, then it is hard to tell the difference between a reading of 400 mV as the actual response or the sensor is fouled such that the reading is compromised. Since there is no other independent measurement to differentiate a fouled sensor versus a good sensor, the user can only assume the reading is a true indication of the reaction rate. Another example of the short comings of prior art methods, these methods can have slow response times when measuring the ORP of species in which the reaction measured involves a two-step electron transfer process. In prior art methods, there is no convenient way to tell if a slowly increasing response is caused by the sensor or by the complexity of the two electrons transfer process. Previously, there was no known method for those skilled in the art to overcome these challenges.